data: Don't race with vendor nvidia driver at startup

The vendor nvidia driver has two modules loaded
at startup.

It's not uncommon for the second module to still
be loading when GDM starts.

Our udev rule relies on the second module to set
up GDM's boot configuration.

This commit adds some synchronization to stall
GDM a bit if the vendor driver is still coming
up.

https://gitlab.gnome.org/GNOME/gdm/-/issues/763

4 files changed, 40 insertions, 1 deletions

diff --git a/data/61-gdm.rules.in b/data/61-gdm.rules.in
index e9c72697..9451c12e 100644
--- a/data/61-gdm.rules.in
+++ b/data/61-gdm.rules.in
@@ -9,6 +9,15 @@ DRIVERS=="simple-framebuffer", GOTO="gdm_nomodeset_end"
 IMPORT{cmdline}="nomodeset", GOTO="gdm_disable_wayland"
 LABEL="gdm_nomodeset_end"
 
+# The vendor nvidia driver has mutiple modules that need to be loaded before GDM can make an
+# informed choice on which way to proceed, so force GDM to wait until NVidia's modules are
+# loaded before starting up.
+KERNEL!="nvidia", GOTO="gdm_nvidia_end"
+SUBSYSTEM!="module", GOTO="gdm_nvidia_end"
+ACTION!="add", GOTO="gdm_nvidia_end"
+RUN+="@bindir@/touch /run/udev/gdm-waiting-on-udev"
+LABEL="gdm_nvidia_end"
+
 # Disable wayland when nvidia modeset is disabled or when drivers are a lower
 # version than 470,
 # For versions above 470 but lower than 510 prefer Xorg,
@@ -30,10 +39,14 @@ GOTO="gdm_end"
 
 LABEL="gdm_prefer_xorg"
 RUN+="@libexecdir@/gdm-runtime-config set daemon PreferredDisplayServer xorg"
-GOTO="gdm_end"
+GOTO="gdm_stop_waiting_on_udev"
 
 LABEL="gdm_disable_wayland"
 RUN+="@libexecdir@/gdm-runtime-config set daemon WaylandEnable false"
+GOTO="gdm_stop_waiting_on_udev"
+
+LABEL="gdm_stop_waiting_on_udev"
+RUN+="@bindir@/rm -f /run/udev/gdm-waiting-on-udev"
 GOTO="gdm_end"
 
 LABEL="gdm_end"
diff --git a/data/gdm-waiting-on-udev.path.in b/data/gdm-waiting-on-udev.path.in
new file mode 100644
index 00000000..ceb03704
--- /dev/null
+++ b/data/gdm-waiting-on-udev.path.in
@@ -0,0 +1,12 @@
+[Unit]
+Description=Synchronize GNOME Display Manager with udev
+ConditionPathExists=/run/udev/gdm-waiting-on-udev
+
+[Path]
+PathChanged=/run/udev/gdm-waiting-on-udev
+Unit=gdm.service
+
+[Install]
+WantedBy=graphical.target
+
+
diff --git a/data/gdm.service.in b/data/gdm.service.in
index 17e8a8de..effdf56a 100644
--- a/data/gdm.service.in
+++ b/data/gdm.service.in
@@ -19,6 +19,11 @@ After=rc-local.service plymouth-start.service systemd-user-sessions.service
 # for any reason, make sure plymouth still stops
 OnFailure=plymouth-quit.service
 
+# If our udev rule is still trying to figure out the lay of the land
+# then block for a bit. gdm-waiting-on-udev.path will start us later
+# when appropriate.
+ConditionPathExists=!/run/udev/gdm-waiting-on-udev
+
 [Service]
 ExecStart=${sbindir}/gdm
 KillMode=mixed
diff --git a/data/meson.build b/data/meson.build
index 2dec4c23..8764abfe 100644
--- a/data/meson.build
+++ b/data/meson.build
@@ -149,6 +149,7 @@ gdm_rules = configure_file(
   output: '@BASENAME@',
   configuration: {
     'libexecdir': gdm_prefix / get_option('libexecdir'),
+    'bindir': gdm_prefix / get_option('bindir'),
   },
   install_dir: udev_dir,
 )
@@ -185,6 +186,14 @@ configure_file(
   format: 'cmake'
 )
 
+configure_file(
+  input: 'gdm-waiting-on-udev.path.in',
+  output: '@BASENAME@',
+  configuration: service_config,
+  install_dir: systemd_systemunitdir,
+  format: 'cmake'
+)
+
 gdm_gnome_session_wanted_targets = []
 foreach component: gdm_gnome_user_session_wanted_components
   gdm_gnome_session_wanted_targets += 'Wants=@0@.target'.format(component)